Local and Systemic Effects of Photobiomodulation Therapy on Muscle Performance and Recovery Post-exercise.

A total of 30 healthy male non-athletes, between 18-35 years, will be randomly divided into 3 experimental groups, named "Placebo (Control)", "Local", "Systemic", according to the lower limb who will receive photobiomodulation therapy. Firstly, a blood collection will be performed by a nurse with sterile and disposable materials for posterior analysis of creatine kinase (CK) and Blood Lactate (BL). Delayed onset muscle soreness (DOMS) will be assessed with the Visual Analogue Scale (VAS) using a 10 cm line. Participants will be instructed to mark the line where their pain best fits at that time (0=no pain, 10=worst pain).Then, the maximum voluntary contraction test (MVC) will be performed, which will consist in performing 3 times of 5-sec isometric contractions of the non-dominant knee extensors in the isokinetic dynamometer device. During the execution of the MVC, the participants will be verbally encouraged to exert the greatest force at that moment. Photobiomodulation therapy will be applied 2 minutes after the MVC test in six points of non-dominant anterior thigh muscle. After irradiation, participants will perform the protocol of eccentric contractions. This protocol will be performed to induce muscle fatigue by resisting the movement of knee flexion in 5 series of 15 repetitions with 30 seconds -intervals (eccentric contractions). Assessments (blood collection, VAS and MVC) will be performed before warm-up (baseline), 1 minute after exercise protocol and 1, 24, 48 and 72 hours after eccentric exercise protocol.